Non-contact temperature sensor for a roll fuser of a xerographic reproduction apparatus

ABSTRACT

Apparatus for fusing toner material to a substrate by passing the substrate between a pair of rollers at least one of which is heated. The surface temperature of the heated roller at an area where it contacts the toner material is maintained at a substantially constant value by means of a non-contact sensor comprising a part of a control for the heated roll.

[ Nov. 19, 1974 United States Patent [191 Abowitz et al.

X on H 00 3 3 1 NON-CONTACT TEMPERATURE SENSOR 3,189,729 6/1965Lusebrink........................... FOR A ROLL FUSER OF A XEROGRAPHIC3,369,106 2/1968 Troll REPRODUCTION APPARATUS 3,654,463 4/1972 Geuslc eta1.

3,697,726 10/1972 Geromme [75] Inventors: Gerald Abowitz, Rochester;3,725,310 4/1973 Donohue......

Frederick Robert Ruckdeschel, 3,735,092 5/1973 Traister......,,.Webster; Robert Eugene Gerace 3,742,191 6/1973 Poole et Fairport, all ofNY.

OTHER PUBLICATIONS D. N. Neal, G. C. Greuling, IBM Technical DisclosureBulletin, Moving Surface Temperature Sensor, Vol. 14, No. 6, November1971 [73] Assignee: Xerox Corporation, Stamford,

Conn.

22 Filed: July 25, 1973 App]. No.: 382,434 Primary Examiner-C. L,Albritton [52] US. 219/216, 219/471, 338/15 [51] Int. Cl. H05b l/00 [58]Field of Search.................... 219/216, 469-471;

References Cited UNITED STATES PATENTS f o t vm 0. m. mm S Cm. m H m u.mo .We m0 F a g aw .m bn w La s llr admD mmw dM Q, e m n C .l mn a toea.m h 33 7 m m 8 SI .mwm rem m w y mba 2,627,182 Quereau et a1. 338/25 X3,093,744 250/239 S C. R.

CONTROLLER A.C. TO D.C.

CONVERT LAMP SOURCE PATENTE 510v 1 91914 sum 1 or a PATENI'E rm 1 91914sum 2 or 3 PATENTE HEY I 9 I974 NEH 3m 3 I I u.v.

HEAT HEAT LIGHT FUSER l SILICONE l PHOSPHOR l u.vv

LA MP RUBBER RoI I STRIP LAMP VISABLE LIGHT REG. zav us.

58 56 4a 59 I I s. c. R. PHOTORESISTIVE POWER AMPLIFIER CONTROLLER 7CELL SUPPLY CONTROL RES. T VOLTAGE CHARGE I20 v. I20 v.

A0. T0 0.0. s. c. R.

CONVERT V CONTROLLER 46 LAMP SOURCE ROLL FUSER OF A XEROGRAPHICREPRODUCTION APPARATUS BACKGROUND OF THE INVENTION This inventionrelates, in general, to heated roll fuser apparatus for affixing tonermaterial to a substrate to form permanent images thereon and, moreparticularly, to means for controlling the power input to the heatedroll for maintaining substantially constant the surface temperature ofthe heated roll at an area where it contacts the toner material.

In the process of xerography, a light image of an original to be copiedis typically recorded in the fonn of a latent electrostatic image on aphotosensitive member with subsequent rendering of the latent imagevisible by the application of electroscopic marking particles, commonlyreferred to as toner. The visual image can be either fixed directly uponthe photosensitive member or transferred from the member to a sheet ofplain paper with subsequent affixing of the image thereto.

In order to permanently affix or fuse an electroscopic toner materialonto a support member by heat, it is necessary to elevate thetemperature of the toner material to a point at which the constituentsof the toner material coalesce and become tacky. This action causes thetoner to be absorbed to some extent into the fibers of the supportmember which in many instances constitutes plain paper. Thereafter, asthe toner material is cooled, solidification of the toner materialoccurs causing the toner material to be firmly bonded to the supportmember.

In both the xerographic as well as the electrographic recording arts,the use of thermal energyfor fixing toner images onto a support memberis old and wellknown.

One approach to thermal fusing of electroscopic toner images onto asupport has been to pass the support with the toner images thereonbetween a pair of opposed rollers, at least one of which is eitherexternally or internally heated. In this type of arrangement, the tonerimage contacts the surface of the heated roller member in the nipbetween rollers to thereby produce heating of the toner image within thenip.

In apparatus utilizing a fuser roll pair as described above, it isimportant that the heated roll surface be maintained within a suitablerange to properly fuse the toner image to its paper support sheet. Theforegoing is accomplished in a conventional manner by the employment ofa temperature sensitive resistance device commonly referred to as athermistorwhich is placed in physical contact with the heated roll.

In a conventional roll fuser, the fuser roll or heated member is almostalways provided with a release agent applied to the surface thereof inorder to prevent offsetting of toner material to the fuser roll. Therelease agent is, at least at the time that the application to the fuserroll has been accomplished, in the form of a liquid and has the effectof minimizing the thermal energy generated by frictional forces due torubbing between the fuser roll surface and the thermistor.

Where, as in the case of the present invention, the fuser .roll surfacecomprises an elastomeric or other highly susceptible heat generatingmaterial that does not have a release agent applied to the surfacethereof, the heat developed due to friction has a considerable effect onthe temperature sensing device. For example, if the control setting ofthe temperature sensor is at a particular setting corresponding to thetemperature of the fuser roll desired, the temperature sensor due tofrictional forces will sense temperatures on the order to 20 higher thanthe actual surface temperature of the fuser roll. As will beappreciated, this creates all sorts of problems resulting in anunsatisfactory control of the fuser device.

One solution to the problem would be to set the control temperature ofthe sensor or probe at a setting 20 higher than that to which the fuserroll surface is to be maintained, in an area just preceding the nip.This would result in an elevated temperature resulting in *overshoot"presenting the problem of hot offsetting" as well as causing drying outof the paper resulting in paper curling leading to paper jams orpotential fire hazards.

Overshoot occurs when the temperature sensor shuts off the fuser heater,due to the fact that the thermal energy accumulated at the center of thefuser roll continues after heater deenergization to be transferredradially outward to the surface of the fuser roll. Hot offsetting occurswhen the surface of the fuser is raised to a level sufficient to meltthe toner particles thereby creating a condition where the tonermaterial splits resulting in some of the toner being picked up by thefuser roll surface.

Other solutions to the problem have been envisioned but they haveresulted in more expensive or more complicated control devices thanwarranted by other'machine requirements.

Accordingly, it is a primary object of this invention to provide a newand improved electrostatic reproducing apparatus employing heat to fusetoner images to the support paper.

Another object of this invention is to provide a new and improved fusingdevice for an electrostatic copier wherein toner images are formed on acopy paper.

Still another object of the present invention is to provide a new andimproved fusing device for a xerographic reproducing apparatus includinga novel method of controlling the surface temperature of the fuser roll.

Yet another object of this invention is to provide a new and improvedthermal fusing device for xerographic reproducing apparatus wherein theimprovements in the fusing device are accomplished by the provision of anon-contact sensor.

A BRIEF DISCLOSURE OF THE INVENTION Briefly, the above-cited objects areaccomplished by the provision of a non-contact sensor and controltherefor for maintaining the temperature of the fuser roll substantiallyconstant in an area where it contacts toner material.

More specifically, the objects of the present invention are accomplishedby the provision of a photodiode for measuring the light output of aphosphor material which in one embodiment of the invention is formedintegrally with the surface of the fuser roll. Since the light emissionsfrom the phosphor material can be correlated to the temperature of thephosphor material which in turn is a function of the surface temperatureof the roll, the surface temperature can be accurately measured and usedfor controlling the power input to the fuser roll for the purpose ofmaintaining the temperature thereof, substantially constant.

In other embodiments of the invention, the phosphor material maycomprise a part of a device which is mounted adjacent the fuser roll andwhose light emissive characteristics are measured in the same manner asmentioned above.

Where the phosphor material is an integral part of the fuser roll, itmay be uniformly dispersed throughout the surface of the fuser roll ormay constitute a continuous or broken stripe about the circumference ofthe roll.

Further objects of this invention, together with additional featurescontributing thereto and advantages accruing therefrom, will becomereadily apparent from the following description of the preferredembodiment of the invention when read in conjunction with theaccompanying drawings wherein:

FIG. 1 is a front elevational view of an automatic xerographicreproducing apparatus utilizing the present invention;

FIG. 2 is a perspective view partly in section of a fusing deviceincorporated in the apparatus of FIG. 1;

FIG. 3 is a schematic diagram of a fuser control used in conjunctionwith the fuser apparatus illustrated in FIG. 1;

FIG. 4 is a schematic representation of a modified form of controlillustrated in FIG. 3 for controlling the surface temperature of thefuser roll;

FIG. 5 is a fragmentary view of another modification of the invention;and

FIG. 6 is yet another modification of the invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 1, there isshown an embodiment of the subject invention in a suitable environmentsuch as an automatic xerographic reproducing machine having axerographic plate including a photoconductive layer or light sensitivesurface on a conductive backing and formed in the shape of a drum 10which is mounted on a shaft journaled in a frame to rotate in thedirection indicated by the arrow to cause the drum surface sequentiallyto pass a plurality of xerographic processing stations.

For purposes of the present disclosure, the several xerographicprocessing stations in the path of movement of the drum surface may bedescribed functionally as follows:

A charging station A at which the photoconductive layer of thexerographic drum is uniformly charged;

An exposure station B at which a light or radiation pattern of adocument to be reproduced is projected onto the drum surface todissipate the drum charges in the exposed areas thereof, thereby forminga latent electrostatic image of the copy to be reproduced;

A transfer station B at which the xerographic powder image iselectrostatically transferred from the drum surface to a transfersupport material; and

A drum cleaning and discharge station E at which the drum surface isbrushed to remove residual toner particles remaining thereon after imagetransfer, and at which the drum surface is exposed at a relativelybright light source to effect substantially complete discharge of anyresidual electrostatic charge remaining thereon.

At the transfer station D, a transfer of the xerographic powder imagefrom the drum surface to the sheets of support material is effected bymeans of a corona transfer device 16 which is located at or immediatelyafter the line of contact between support material and the rotatingdrum. In operation, the electrostatic field created by the coronatransfer device is effective to tack the support materialelectrostatically to the drum surface whereby the support material movessynchronously with the drum while in contact therewith. Simultaneouslywith the tacking action, the electrostatic field is effective to attractthe toner particles comprising the xerographic powder image from thedrum surface and cause them to adhere electrostatically to the surfaceof the support material.

Immediately subsequent to the image transfer station, there ispositioned a stripping apparatus 18 for removing the sheets of supportmaterial from the drum surface. The heat stripping apparatus is adaptedto strip the leading edge of the support material from the drum surfaceand to direct it onto an endless conveyor 20 which carries the sheetmaterial to a heated fusing roll apparatus 30. The support material ispassed through a top roll or cylinder 34 and a lower roll 36, which isdisplaceable, to permanently affix or fuse the image by a combination ofheat and pressure. The roll 34 has an outer cover 37 made of siliconerubber or other suitable elastromeric material, supported by a rigidbase 38 and having a thicker elastomeric layer 39 interposedtherebetween.

A quartz lamp 40 and reflector 42 therefor are disposed adjacent thefuser roll 34 and are coextensive with the longitudinal axis of thefuser roll. The lamp 40 has a maximum output of 1100 watts when providedwith power from a volt-60 cycle source. With an 1,100 watt output, thelamp can raise the surface temperature of the fuser roll 34 to a levelwhich will cause coalescence of the toner particles which level, as willbe appreciated, will vary in accordance with the thermal characteristicsof the toner material employed. With such an arrangement, the surfacetemperature of the fuser roll will be on the order of 200 to 400F. Theactual output from the lamp will be controlled in accordance with theactual temperature of the roll surface and with the desired temperature.To this end, the roll as illustrated in FIG. 2 contains a stripe 44 ofthermographic phosphor material and a source 46 of ultraviolet light ispositioned adjacent to the roll 34 such that the phosphor material isexcited by the ultraviolet light. An electro-optical detector, forexample, a photoresistive member or cell 48 is also supported adjacentthe fuser roll 34 such that the light emissions from the phosphor stripeare presented thereto for purposes to be explained hereinbelow,Thermographic phosphors have the property that when excited byultraviolet light, they emit visible light, the intensity of which isdependent upon the density recombination levels near the valance bandedge. A rise in temperature of the phosphor with a constant source of UVreduces the number of levels available for radiative recombination andthereby diminishes the light output. Several such phosphors areavailable from US. Radium Company under the trade name Radelin. Themid-range brightness of such phosphors is on the order of l erg. per cmsecond which is easily detected by inexpensive commercially availablephotodiodes. The-sensitivity of these materials in l5percentK.

While the phosphor material which is integral with the fuser roll 34, isillustrated as being applied to the surface of the roll in the form of acontinuous stripe around the circumference, it will be appreciated thatit could be applied to the whole surface or a broken or segmented stripe(FIG. 4) or as a single spot. Clear RTV compounds have been foundsuitable as binder materials for the phosphor.

The source 46, preferably a 2 watt UV lamp commercially available fromthe General Electric Company, and the photoresistive member 48 may asshown in FIG. 2, be contained in a common holder 50 fabricated fromaluminum or other suitable material. When so mounted, the light emittedfrom the phosphor is transmitted by a fiber bundle 52 to thephotoresistive member 48.

FIG. 3 illustrates a closed loop control system wherein the outputsignal (corresponding to the roll surface temperature) of thephotoresistive cell 48 is amplified by an amplifier 56, the amplifiedsignal being transmitted to an SCR controller 58 which provides power tothe lamp 40 in accordance with the temperature sensor and the resultingsignals generated. In operation, the heat raises the surface temperatureof the roll to a point where the amplified signal approaches the setpoint of the SCR resulting in the reduction of power to the lamp therebymaintaining the fuser temperature to a substantially constant value.Surface temperature control within plus or minus 2F. has been obtainedunder constant thermal loading. A power supply 59 providing a regulated28 volt D.C. supply is provided for the UV lamp 46.

FIG. 4 illustrates a modified form of the invention wherein the fuserroll 34 is replaced by a roll 60 having segments 62 of phosphor materialextending about the circumference of the roll 60. Unlike the DC. signalgenerated by the continuous stripe 44, the segments 62 will generatesinusoidal signals which have the advantage of an AC. amplifier which ismore stable than the DC. signal and a more even temperature gradientacross the broken path formed by the segments 62. In this embodiment,the A.C. signal from a photoresistive element 64 is preamplified in apreamplifier 66 with subsequent amplification by an amplifier 68. TheAC. signal is converted by an A.C. to DC. converter 70 and transmittedto an SCR controller 72 which as in the case of the embodiment of FIG. 3is utilized to regulate the output of the lamp.

As illustrated in FIG. 5, the phosphor material need not form anintegral part of the fuser roll but may form a part of a thin,heat-resistant substrate 76, for example, mica, which is disposedadjacent to the surface of a fuser roll 78. In this case, the detectorand signal generator is in the form of a photodiode 80 having a UVattenuator 82 (glass) at the entrance thereof.

Asillustrated in FIG. 6, the phosphor may form an integral part of anelectroluminescent panel 86 also positioned adjacent the fuser roll 78.

While the invention has been described with reference to specificembodiments disclosed, it will be appreciated that certain modificationswill appear to those skilled in the art without departing from thespirit and scope of this invention. It is, therefore, intended that theinvention not be limited by the embodiments disclosed but that theprotection sought be limited only by the claims appended hereto whichwould include those modifications mentioned above.

What is claimed is:

l. Fuser apparatus comprising:

a first roller;

a second roller cooperating with said first roller to form a nip throughwhich a substrate supporting toner material is moved;

means for heating at least one of said rollers to elevate the surfacetemperature thereof to a level sufficient to render the toner materialtacky;

means out of contact from said at least one of said rollers for sensingthe surface temperature thereof; and

means responsive to the temperature sensed for controlling said heatingfor maintaining the surface temperature of said at least one of saidrollers constant in an area where the toner material is contactedthereby, said means for sensing temperature comprising means forconverting thermal radiation to light radiation representative of saidsurface temperature whereby said temperature sensing means senses saidlight radiation.

2. Apparatus according to claim 1 wherein said sensing means comprisesmeans for generating electrical signals representative of thetemperature of said at least one roller.

3. Apparatus according to claim 2 wherein said converting meanscomprises a phosphor material and means for exciting said phosphormaterial to thereby emit visible radiation, said phosphor material beingso disposed relative to said at least one roller as to receive thermalenergy therefrom in accordance with the temperature thereof.

4. Apparatus according to claim 3 wherein said phosphor materialcomprises a continuous stripe about the circumference of said at leastone roller.

5. Apparatus according to claim 3 wherein said phosphor materialcomprises a plurality of segments extending about the circumference ofsaid at least one roller.

6. Apparatus according to claim 3 wherein said phosphor materialcomprises a substrate positioned adjacent said at least one roller.

7. Apparatus according to claim 3 wherein said phosphor materialcomprises an electroluminescent panel positioned adjacent said at leastone roller.

1. Fuser apparatus comprising: a first roller; a second rollercooperating with said first roller to form a nip through which asubstrate supporting toner material is moved; means for heating at leastone of said rollers to elevate the surface temperature thereof to alevel sufficient to render the toner material tacky; means out ofcontact from said at least one of said rollers for sensing the surfacetemperature thereof; and means responsive to the temperature sensed forcontrolling said heating for maintaining the surface temperature of saidat least one of said rollers constant in an area where the tonermaterial is contacted thereby, said means for sensing temperaturecomprising means for converting thermal radiation to light radiationrepresentative of said surface temperature whereby said temperaturesensing means senses said light radiation.
 2. Apparatus according toclaim 1 wherein said sensing means comprises means for generatingelectrical signals representative of the temperature of said at leastone roller.
 3. Apparatus according to claim 2 wherein said convertingmeans comprises a phosphor material and means for exciting said phosphormaterial to thereby emit visible radiation, said phosphor material beingso disposed relative to said at least one roller as to receive thermalenergy therefrom in accordance with the temperature thereof. 4.Apparatus according to claim 3 wherein said phosphor material comprisesa continuous stripe about the circumference of said at least one roller.5. Apparatus according to claim 3 wherein said phosphor materialcomprises a plurality of segments extending about the circumference ofsaid at least one roller.
 6. Apparatus according to claim 3 wherein saidphosphor material comprises a substrate positioned adjacent said atleast one roller.
 7. Apparatus according to claim 3 wherein saidphosphor material comprises an electroluminescent panel positionedadjacent said at least one roller.